Added some formatting to the image processor.

The image processor was throwing errors that were not descriptive enough. They are now throwing more descriptive errors.
Optimized the survey response queries.

The survey response queries should now be much more efficient.

References #451
Removed an unused debugging file.

A reference to an unused debugging file in the EasyPost page was removed.

Closes #561
Merge branch 'ohmage-2.16' of github.com:ohmage/ohmageServer